feat(auth): add @RequiresHouseholdRole annotation with interceptor

Reusable annotation for planner-only endpoints. Uses a
HandlerInterceptor that resolves the household role from the
authenticated user and throws 403 if the role doesn't match.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/main/java/com/recipeapp/common/RequiresHouseholdRole.java

@@ -0,0 +1,12 @@
+package com.recipeapp.common;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+@Target(ElementType.METHOD)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface RequiresHouseholdRole {
+    String value();
+}